A detailed chemical study is being made of the lipid composition and of the metabolism of lipids in reproductive tissue of male animals, particularly the rat. The biosynthesis and interconversion of fatty acids is being studied in tests of rat, both in vivo and in vitro, using slices and subcellular fractions. These processes will also be investigated in separated cell types. The changes brought about in these metabolic processes by age, diet, pathological conditions, and hormonal influences will be determined. Findings in the studies of lipid composition and metabolism are supplemented with histological studies of the tissue.